The problem of sand production into a wellbore is illustrated in FIG. 1. As shown in FIG. 1, the upper casing 10 supports middle casing 12, which in turn supports a lower casing 14. The support mechanism is typically a hanger 16, which is of atype well-known in the art. Inside the wellbore W, formed by the casing sections 10, 12, and 14, is the production tubing 18, which extends through a packer 20. Casing 14 can be closed off by a bridge plug 22. Casing 14 is perforated, as indicated by perforations 24. This is accomplished by perforating guns of known design or by other means. Thus, the producing zone 26 communicates with the wellbore W through the perforations 24. Eventually, the fluids produced from the zone 26 bring sand 28 into the wellbore, as shown in FIG. 1.
In the past, there have been numerous techniques that have been used to try to remove the sand 28 from the wellbore W. In one technique, the packer 20 can be pulled and with it the tubing string 18. Thereafter, coiled tubing can be run in the wellbore to the zone adjacent the sand 28 and vigorous circulation through pumping through the coiled tubing initiated in an effort to get the sand to come up to the surface. The problem with this technique is that it is time-consuming and generally ineffective. The reason is that as the fluid exits the coiled tubing and agitates the sand 28, it may be successful in moving the sand 28 uphole to a certain extent. However, as the casing sections become bigger, the velocity uphole in the wellbore W decreases and precipitates the sand. Thus, using this technique, very little sand is effectively removed.
U.S. Pat. No. 4,924,940 illustrates another technique for removal of sand from a wellbore. Here, a design involving multiple flapper-type valves and a reciprocating piston are used to bring the sand within the valves where it is trapped. This device can be combined with a retrievable packer to isolate a portion of the wellbore for accomplishing the sand collection below. This design involves numerous moving parts and is fairly complicated to assemble and effectively operate. A related design of the Cavins Corporation, referred to as the "Sand Trap Downhole Desander" employs a seal to isolate the wellbore, below which are a series of inlet slots. Internally, the device uses a liquid cyclone effect to separate sand entrained in the liquid. A downhole pump is part of the bottomhole assembly and its suction draws out the fluid out the top, with the sand being captured at the bottom. The fluid with the sand flows down and then makes a turn up to get into the pump.
Other devices rely on a jetting or eductor action such as the Baker Oil Tools combination ball-type jet and junk basket, Product No. 130-97. This product has a series of movable members which are deflected by the junk which is brought into the basket region. The eductor induces flow through the bottom of the tool, past the pivoting fingers which form the basket. This tool is generally designed to catch larger debris such as cuttings from milling packers and other downhole equipment that needs to be removed from the wellbore. This product, when used for sand, will generally allow some of the captured sand to pass back out through the pivoting segments that form the basket. Additionally, if circulation is stopped, sand can get behind the pivoting segments, thus preventing them from opening all the way to facilitate flow therethrough.
Another product from Baker Oil Tools is a combination of a jet bushing, Product No. 130-96, and an internal boot basket, Product No. 130-21. When combined, a jet action is used to induce fluid flow into the tool laden with sand. The internal boot basket has a series of inclined plates which create a circuitous path for the fluid induced into the housing through the action of the jet or eductor. While making the various twists and turns so that the fluid can exit the tool, the sand drops out and is caught on the inclined internal plates. The various internal boot basket sections are threaded through each other and ultimately to the jet bushing. An internal screen is provided for the fluid exiting the tool. The exit of the tool goes around the jet and back into the annulus.
Yet another design from Baker Oil Tools is the Model M reverse circulating tool which employs a cup seal to close off the wellbore, and a reverse circulating Towpath below the cup seal which brings into the central bore of the tool the reverse circulating fluid laden with the debris to be trapped within the body of the tool. Ultimately, the reverse circulating fluid exits the body of the tool above the cup seal and flows to the surface in the annulus. This tool employs the junk basket design previously designed for the other Baker Oil Tools models or other modified designs relying on the principal of velocity reduction to precipitate the sand.
What has been lacking in these prior designs is a tool that can be assembled and disassembled quickly. Rig time is a significant concern in view of the ever-increasing daily rates now being charged. Thus, these prior designs, which were put together by attaching threaded components, took significant times to assemble for run-in and to disassemble when filled and brought to the surface. Thus, it is one object of the apparatus and method of the present invention to be able to assemble the tool for run-in quickly and disassemble it upon retrieval in short order so as to reduce required rig time.
It is a further object of the invention to be able to run the sand retrieval tool through tubing, supported on coiled tubing or on electric line. It is a further object of the invention to provide a simple design with the fewest number of parts that move so that reliable operation can be achieved. Those and other benefits of the apparatus and method of the present invention will be appreciated by those of ordinary skill in the art by a review of the description of the preferred embodiment below.